Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

Basal Ganglia (Short note/long question)

Introduction:

It is a number of nuclear (grey matter) masses which lie within the cerebral hemisphere.

They consists of :

Caudate nucleus

Lentiform nucleus : Putamen and Globus pallidus

Amygdaloid nucleus

Claustrum.

Corpus striatum: Caudate nucleus and putamen part of lentiform nucleus form corpus striatum (Neostriatum) (They are known as corpus striatum due to appearance of alternating band of grey and white matter at fused part of head of caudate nucleus and putamen with fibers of internal capsule).

Globus pallidus in part of paleostriatum.

(No need to draw this diagram- only for understanding)

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

Caudate nucleus: (*****Important - Viva)

It is “C” shape nucleus located medial to internal capsule projecting in the cavity of lateral ventricle.

Parts of Caudate nucleus:

1. Head: located in the floor of anterior horn of lateral ventricle and partly fused with putamen of lentiform nucleus.

2. Body: located in the floor of central part of lateral ventricle.

3. Tail: Tapering part located in the roof of inferior horn of lateral ventricle and connected to amygdaloid nucleus

(Draw this Diagram for the short note)

Lentiform nucleus: (*****Important - Viva)

It is biconvex lens shape nucleus located lateral to internal capsule.

Parts of lentiform nucleus:

1. Putamen: lateral and dark coloured nucleus and partly fused with head of caudate nucleus.

2. Globus pallidus: medial and pale coloured nuclus.

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

Amygdaloid nucleus:

It is small nucleus located in the roof of inferior of lateral ventricle.

Claustrum:

It is strip of grey matter lateral to lentiform nucleus.

Connections of Basal Ganglia:

Connections and neurotransmitters of Corpus striatum:

Afferent fibers:

1. Corticostriate fibers: from cortex of cerebrum to corpus striatum (Caudate nucleus and putamen). Glutamate is neurotransmitter and excitatory to corpus striatum

2. Nigrostriatal fibers: from substantia nigra (Midbrain) to corpus striatum (Caudate nucleus and putamen). These are dopaminergic neurons and inhibitory to corpus striatum and degeneration of these neurons leads to Parkinson’s disease.

Efferent fibers:

1. Striatonigral fibers: from corpus striatum (Caudate nucleus and putamen) to substantia nigra (Midbrain).

2. Striatopallidal fibers: from corpus striatum (Caudate nucleus and putamen) to globus pallidus. GABA is neurotransmitter and inhibitory to globus pallidus.

Connections of Globus pallidus:

Afferent fibers:

1. Striatopallidal fibers: from corpus striatum (Caudate nucleus and putamen) to globus pallidus.

Efferent fibers:

1. Pallidothalamic fibers: From Globus pallidus to thalamus via ansa lenticularis or lenticularis fasciculus and from thalamus they go to cortex of cerebrum via thalamocortical radiation.

2. Pallidosubthalamic fibers: From Globus pallidus to subthalamus and from subthalamus.

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

(Draw this Diagram for the short note)

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

(No need to draw this diagram- only for understanding)

Function of Basal ganglia:

1. Their function is to facilitate purposeful behaviour and movements and to inhibit unwanted or inappropriate (not suitable ) movements.

2. They are also responsible for synchronized movements of limbs e.g. swinging of arms while walking.

3. Amygdaloid nucleus is concerned with aggressive behavior.

Ojvensha E learning Resources-Prepared by Dr.B.B.Gosai

Applied Anatomy of Basal ganglia:

1. Huntington’s Disease

It is an degenerative autosomal dominant inherited disease with the onset occurring in adult life. Within the striatum, there is progressive degeneration of the globus pallidus ( indirect segment ).

Choreiform movements first appear as involuntary movements of the extremities and twitching of the face (facial grimacing).

Progressive dementia occurs with loss of memory and intellectual capacity There is degeneration of the GABA; P-secreting and acetylcholine-secreting.

2. Parkinson’s disease

It is a neurodegenerative disease of elderly, of unknown cause. It is characterized by akinesia, flexed posture, rigidity and a resting tremor and mask like face.

It is due to loss of striatal dopamine levels. It is treated by levodopa which restores normal striatal function

3. Sydenham’s Chorea ( St Vitus’ dance )

The patient exhibits involuntary, quick, jerky, spasmodic, irregular movements that are nonrepetitive. Sudden movements of the head; trunk or limbs. It is a common manifestation of rheumatic fever.

4. Hemiballism

Sudden choreiform movements of the limbs on one side of the body. It caused by a lesion of contralateral subthalamic nucleus.

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